1. Field of the Invention
This invention relates to a lactic acid bacterium, and more particularly relates to a novel lactic acid bacterium strain having immunomodulatory and anti-allergic effects in a subject.
2. Description of Related Art
Allergic disorders, such as allergic rhinitis, atopic dermatitis, allergic asthma and food allergies, have become increasingly prevalent in many countries. These disorders not only affect the individual's life quality but also become a medical burden on society. Allergies are related to the T-helper cell type 2 (Th2) responses in both T-cells and B-cells. Th2 responses are characterized by the production of certain cytokines including interleukin (IL)-4, -5, -13, and the production of total immunoglobulin (Ig) E, antigen-specific IgE and IgG1. Th2 cytokines produced by Th2 cells enhance IgE production and eosinophil accumulation. Among the Th2 cytokines, IL-5 is known to be important to the differentiation, maturation and recruitment of eosinophils while both IL-4 and IL-13 are promising targets for therapeutic intervention in asthma and other Th2-associated diseases. Furthermore, IL-13 directly enhances mucus hypersecretion and airway hyperresponsiveness (AHR). Cytokine production is regarded as T-cell response while immunoglobulin production is regarded as B-cell response. Th1 cells can suppress Th2 responses by secreting interferon (IFN)-γ, IgG2a, IL-2, and IL-3. Therefore, to regulate the immune responses by suppressing Th2-responses while enhancing Th1-responses is expected to be helpful in the treatment of allergy and other Th2-dominant disorders, such as asthma which is a chronic, complex respiratory disease caused by various airway obstructions, airway eosinophil inflammation and bronchial hyperresponsiveness.
Numerous studies have proposed that lactic acid bacteria (LAB), either live or heat-killed, alleviate allergic symptoms by modulating Th1/Th2 responses toward a Th1-dominant state. For example, live Lactobacillus paracasei KW3110 was orally administered to allergic mice and the results revealed anti-allergic effects on both Th1 and Th2 cytokines including IL-12 induction and IL-4 repression. Heat-killed Lactobacillus casei strain Shirota (LcS) stimulated IL-12 secretion, which shifted the cytokine production pattern from a Th2 to a Th1 predominance and thereby suppressed IgE production, IgG1 responses and systemic anaphylaxis in human. Heat-killed Lactobacillus brevis SBC8803 inhibited IgE production and histamine secretion due to the improvement of the Th1/Th2 balance toward Th1 dominance. Heat-treated Lactobacillus acidophilus strain L-55 was orally administered to ovalbumin (OVA)-sensitized BALB/c mice and the results showed inhibiting the nasal symptoms, sneezing and nasal rubbing induced by OVA challenge. Thus, either live or heat-killed LAB exhibits the capacity to ameliorate allergic responses in murine or in human.
In the present invention, Lactobacillus plantarum subsp. plantarum K37 (hereinafter referred to K37), isolated from fu-tsai, traditional fermented mustard products of Taiwan, is selected because of its profound immunomodulatory potency in vitro by inducing higher levels of IFN-γ production in human peripheral blood mononuclear cells (hPBMCs). Different amounts of K37, such as 105, 107, and 109 CFU (colony forming unit), are orally administered to OVA-sensitized and OVA-challenged BALB/c mice. The effects of K37 on systemic allergy are investigated by determining serum levels of Igs and cytokines. The AHR against methacholine is evaluated using non-invasive whole body plethysmography. The histological analysis is also assessed.